For future reference, and a hat tip to villajk for alerting me to this in the first place, if it's possible to break your journey up and get day returns on stops along the way, you might find a way of getting there cheaper. Sunderland might be a bit of a long haul for it to be practical but if you look at getting tiickets between Birmingham/Derby, Derby/Sheffield, Sheffield/York, York/Durham, Durham/Sunderland or something like that, it might be doable. Try plotting the route on a spreadsheet to explore all variables and options.